This invention relates to irrigation equipment, and more particularly to a hose for drip or trickle irrigation, of the type having a primary duct of large cross-section, at least one secondary duct of small cross-section, and inlet and outlet ports causing the primary duct to communicate with each secondary duct, on the one hand, and the latter to communicate with the outside, on the other hand. The invention further relates to a method and an installation for producing such a hose.
Drip irrigation is a method of cultivation which is finding increasingly widespread application in countries desirous of boosting their agricultural or horticultural output. In this method, specially designed hoses are placed in the cultivated areas in such a way that they can be continuously supplied with water under pressure and can, in turn, supply a trickle of water at the base of each plant. Hoses must thus be placed along each row of plants so that a nozzle allowing water to drip out is situated close to each plant. Hence these nozzles must be distributed along the hoses at distances corresponding to the spacing between the plants. In general, such hoses are of plastic and can thus be wound up on reels or revolving stands when not in use. Some examples of the prior art are found in the published French Patent Application Nos. 2,409,795 and 2,386,983, as well as in European Patent Application Publication Nos. 0 091 059 and 0 069 487, all of which describe various designs of such irrigation hoses.
It is an object of this invention to provide an improved drip irrigation hose in which the rate of flow from each outlet port can be precisely predetermined.
A further object of this invention is to provide a drip irrigation hose having outlet ports spaced along the hose at intervals corresponding to the distance between the plants to be irrigated so that the water will flow directly toward each plant.
Another object of this invention is to provide a drip irrigation hose by means of which the rate of flow from each port is so regulated that each plant receives substantially the same amount of water.
To this end, the hose according to the present invention comprises a first tube constituting the primary duct and a second tube extending around the primary duct to form an outer covering, at least one of the tubes including at least one longitudinal groove capable of delimiting, with the other tube, a secondary duct, the first tube including inlet ports disposed at intervals and opening into the secondary duct or ducts, and the outer covering including, disposed at intervals, outlet ports from the secondary duct or ducts interposed between the inlet ports.
Still another object of this invention is to provide an improved method of producing drip irrigation hoses more rapidly, more reliably, and considerably more economically than has heretofore been possible, as well as an installation for carrying out such a method.
To this end, in the method according to the present invention, a first tube and a second tube are continuously formed at different locations, the first tube is brought to the formation location of the second tube, the latter is formed about the former, the first tube is perforated at a location situated between the formation locations of the tubes, and the second tube is perforated at a location situated downstream from the formation locations of both tubes.
The installation according to the present invention comprises two extruders provided with a first and a second extrusion head, respectively, and arranged to produce a first tube and a second tube, respectively, the latter surrounding the former, means for guiding the first tube toward the second extrusion head, means disposed between the two extrusion heads for perforating the first tube, and means disposed downstream from the second extrusion head for perforating the second tube.